1. Field of the Invention
The present invention generally relates to an ozone generating apparatus. More particularly, the invention is directed to implementation of an ozone generating apparatus with a large capacity.
2. Description of Related Art
For having better understanding of the present invention, background techniques thereof will first be described in some detail. FIGS. 25A and 25B show in a sectional view and a front view, respectively, a major portion of a conventional ozone generating apparatus known as the "Otto-Plate" type ozone generating apparatus which is disclosed in "Ozonizer Handbook" edited by the Ozonizer Engineers Group of the Institute of Electronic Engineers of Japan and published by Corona Co. ltd., 1950, p. 249. Referring to the figures, the conventional ozone generating apparatus is comprised of a power source 1, metal electrodes 2 coupled to the ground potential, high-voltage electrodes 3 disposed in opposition to the metal electrodes 2, respectively, and connected to the power source I to be applied with a high voltage, dielectric plates (glass plate) 4 disposed on the surfaces of the metal electrode 2 and the high-voltage electrode 3, respectively, discharge spaces 5 in each of which an electric discharge takes place, spacers 6 formed of an electrically insulating material (dielectric material) and defining the discharge spaces 5, respectively, raw gas supply ports 7, a gas exit port 8 and an ozonized gas discharge pipe 9. The metal electrode 2, the high-voltage electrode 3 and the dielectric plates 4 disposed between the electrodes 2 and 3 cooperate to constitute one discharge cell.
Next operation of the ozone generating apparatus implemented in the above structure will be described below. In the case of the conventional ozone generating apparatus described above, gas discharge holes are formed in the metal electrodes 2, the high-voltage electrodes 3 and the dielectric plate 4 at center portions, respectively. Although no description is found concerning the spacer 6 in the above-mentioned publication, the spacers 6 of a dielectric material are disposed around the discharge space 5 in an array not interfering the gas flow for the purpose of sustaining distance (gap length) between the dielectric plates 4.
A raw gas containing oxygen is introduced into the ozone generating apparatus from the ambient, as indicated by arrows 7. A part of oxygen contained in the raw gas is ozonized when the raw gas passes through the discharge spaces 5 within each of which the electric discharge is taking place under the action of a high voltage applied from the power source 1. The gas containing ozone as generated is taken out as an ozonized gas in the direction indicated by an arrow 8 by way of the ozonized gas discharge pipe 9 disposed at a center portion of the ozone generating apparatus.
As will readily be understood, the electric discharge within the discharge space 5 is accompanied with generation of heat. Consequently, unless the gas flowing through the discharge spaces is cooled effectively, the temperature of the gas within the discharge space 5 increases, involving reduction in the amount of ozone generated. For this reason, the metal electrode 2 and the high-voltage electrode 3 are cooled by using an electrically insulating liquid such as an insulating oil to thereby suppress the gas temperature from increasing.
In order to realize the conventional ozone generating apparatus of the structure described above with a large capacity, a plurality of discharge cells are stacked in plural stages, as is schematically illustrated in FIG. 25A. Obviously, the amount of ozone as generated increases in proportion to the number of the stages of the discharge cells. In the practical applications in the individual field such as water treatment, pulp bleaching and the like, there are usually demanded several ten ozone generating apparatuses each including several ten or more discharge cells. Consequently, in the implementation of an ozone production system of a large capacity, the number of the electrodes as well as the number of the parts required for the assembling increases in proportion to the number of the stages of the ozone generating cells and/or the number of the ozone generating apparatus as employed, which will of course incur not only a high manufacturing cost but also a large space for installation and difficulty in effecting the maintenance or other services.
In this conjunction, it is also noted that the amount of ozone generated can be increased by increasing the electric discharge area of each discharge cell. However, when the diameter of the electrode is increased excessively, there will arise a problem that the thickness of the electrode has to be increased remarkably in order to secure a desired flatness of the electrode with a high precision, as a result of which the weight of each electrode will necessarily increase considerably. Besides, it is noted that the dielectric member 4 is usually feeble in mechanical strength, making it difficult to realize a desired flatness. Thus, limitation is imposed to the attempt for increasing the electric discharge area of the electrodes.